Cutaneous squamous cell carcinoma (SCC) is the second most common cancer in America, with over 700,000 cases diagnosed annually, and its incidence is on the rise. Despite the large population affected and resultant burden of disease, little is known about genetic determinants of SCCs. There are no published genome-wide association studies (GWAS) examining single nucleotide polymorphism (SNP) variants associated with SCC risk. The lack of published findings may be due, in part, to the fact that cutaneous SCCs are not reportable malignancies, and are therefore difficult to reliably identify. The electronic pathology databases at Kaiser Permanente Northern California (KNPC) overcome that barrier, and have been used to capture all biopsy-proven cutaneous SCCs from 1997 onward in a validated SCC registry. This project utilizes existing genetic data on over 675,000 SNPs from a large, well-characterized cohort of the Research Program on Genes, Environment and Health (RPGEH). The RPGEH has also collected comprehensive data including information on demographic and environmental variables on its cohort members. Using the unique resources of the RPGEH combined with the SCC Registry, we aim to perform a GWAS to identify SNP sequence variants associated with SCC risk on 77,578 non-Hispanic white RPGEH members, 5,953 of whom go on to develop at least one post-enrollment SCC. We will also test for interactions with established SCC risk factors, including pigmentation, gender, smoking, and actinic keratosis (a clinical marker for chronic ultraviolet light exposure). Furthermore, we will determine whether our identified SNP associations are stronger in subjects with multiple primary SCCs. In addition, we will evaluate whether there is any variation in SNP effects by tumor characteristics. Finally, we will compare our SNPs with those previously identified for BCCs and melanomas from published GWAS to attempt to identify genetic loci associated with skin cancer risk. Ultimately, we seek to improve our understanding of cutaneous SCCs and to identify mechanisms accounting for increased inherited susceptibility.